1. Field of the Invention
This invention relates to packaging methods and apparatus. Particularly, this invention relates to an apparatus and method for packaging flat and stacked groups of articles into carrying cartons. The apparatus and method are particularly well suited for packaging relatively large groups of small articles in stacked configurations into paperboard cartons.
2. Background of the Invention
Prior art packaging machines include U.S. Pat. No. 4,802,254 to applicants' assignee, Riverwood International Corporation, for a Vertical Cartoning Assembly and Method which discloses the assembly of cartons for pre-selected article groups being moved on a conveyor. U.S. Pat. No. 5,036,644, also to applicants' assignee, discloses a Packaging Sleever Assembly which transfers flat packaging sleeves directly onto pre-selected article groups and subsequently wraps and closes the cartons. U.S. Pat. No. 5,241,806, also to applicants' assignee, discloses a Continuous Motion Cartoner Assembly which loads article groups into open ended carton sleeves. Additionally, applicants' assignee manufactures TWIN STACK.RTM. Packaging Machines, disclosed in U.S. Pat. No. 5,666,789, which form stacked article groups and subsequently load the groups into open ended carton sleeves.
On the TWIN STACK machines, groups of articles, such as cylindrical beverage cans, are arranged in a rectangular array, such as 3 by 4, and placed in a carton. To accomplish this, cans are fed in mass by a conveyer into a series of lanes separated by walls where the cans are aligned with each other. Each lane is wide enough for a single can with little clearance. Multiple lanes are used to create the width of the array, and a selecting mechanism is used to select the number of cans in the lanes to form the length of the array.
On one machine, the TWIN STACK 100.TM., cans are maintained laterally aligned with one another across the lanes by a mechanical device which stops the first can in all lanes at a uniform distance. The selecting mechanism is an indexing type which intermittently allows cans to slide out of the lanes onto a deadplate where a group is formed, then the group is moved away for installation into cartons. The conveyor feeding the cans continues to move, thereby creating pressure on each lane of cans and keeping cans tightly stacked in each lane.
Ideally the conveyor feeding the cans can be used to push the cans onto the deadplate and against a stop which properly locates cans for grouping. However, there is friction between the cans and the walls of the lanes, and frictional load on cans may be different for each lane. When the mechanical device holding the first can in all lanes is released to allow cans to flow onto a deadplate, cans in a lane with lower friction may move faster than cans in a lane with higher friction causing the array to be misaligned on the deadplate. If friction is so high that cans in one lane stick when the others move, the group will be a jumble of the wrong number of misaligned cans. Such an occurrence would typically require stopping the machine to correct the problem.
The solution implemented in the Twin Stack 100.TM. is to use a reciprocating mechanism having a series of stop pins and bars to lead the cans onto the deadplate, group them, and push them into a carton. A first set of pins are driven upward between each lane of cans to stop the movement of cans. Another set of pins are then driven upward between each lane behind a predetermined number of cans to form a group of cans and stop the cans in the infeed lanes from moving when the group of cans is moved. A set of loading pins then moves in behind the group of cans, the first set of pins retracts, and the loading pins move the group of cans forward and into cartons. The first set of pins are then extend again and a staging bar moves into position in front of the cans in the infeed lanes. The second set of pins is retracted and the cans advance forward contacting the bar. The staging bar is then advanced forward, leading the cans to the first set of pins, then the bar is retracted. The staging bar prevents cans in one lane from moving faster than cans in another lane due to frictional differences between lanes lane. The motion of the pins and staging bar must be synchronized with the rest of the packaging machine. This system is relatively complex and may limit the speed at which the packaging machine can run. Applicant's invention provides an apparatus and method for packaging cylindrical articles which is believed to overcome the limitations and shortcomings of the art.
It is an object of this invention to provide an apparatus and method for reliably packaging products in a wide range of flat or stacked group sizes and configurations. Another object of this invention is to provide a packaging apparatus and method which are usable with a variety of package types and sizes, article types and sizes, and group configurations (stacked and unstacked) and sizes. Another object is to provide an apparatus which is low in cost. Another object is to provide an apparatus which is compact. Another object is to provide an apparatus which is optimized for packaging relatively large groups of relatively small articles.